Climate control question for you Ford guys

[BobT]

I have a 2009 F150 Lariat with an intermittent problem. When in "Auto" mode for climate control the fan gets stuck in high speed. It usually starts out fine, with the fan in low speed and then increasing as the engine coolant warms up but then when the computer decides to put the fan into high speed, it gets stuck there. When I push the manual speed control buttons the computer responds by indicating that I am changing speed, which tells me that the logic seems to be functioning, but the fan remains in high speed. If I leave it alone eventually and quite suddenly the fan will drop out of high speed and I have manual control back again. Sometimes if I press the power button and turn off the system completely for a few seconds (10-20) and then turn it back on, it goes back to normal operation. There have been a few times that if I shut the truck off while the fan is stuck in high speed, it will still be stuck when I restart the truck later.

I don't know how this system is programmed or controlled but I've been programming and designing electrical controls for industrial equipment for 20 years and the only thought that I can put to this is that there might be some kind of control relay that is feezing in a particular state forcing the fan to stay at high speed even though the logic is telling it to do otherwise.

Any thoughts?

Thanks,

[Scott K]

Have the codes checked in the eatc module. Sounds like a bad eatc module to me

[Lip_Ripper Guy]

I'm assuming that you know in 'auto' mode the interior temp and fan speed is controlled by the thermostat (similar to a house)? If that is the case, then I think what you are saying is that the fan speed isn't reacting to the temp hitting it's set point?

So in mine the fan speed starts off low until the truck warms up a little, then goes to high in order to get it up to temp, and then changes to lower once it is up to the set point. If I have my doors open and it gets cold, it bumps the speed back up, and then back down to maintain.

[fish_eat_sleep]

This might sound dumb but if its in full auto mode (fan speed and temp). then you decrease fan speed, the Cabin temp wont keep up. In My moms Honda it does a similar thing with the fan speed if you turn speed down manually but keep temp on auto (it over rides the driver input) but theres a separate AUTO on/off button that fixes that. manual mode also allows you to turn the a/c compressor off. I see your problem may be different but in the honda at least. auto means you pick the temp, the car maintains that temp regardless until auto mode is turned off, which returns full manual fan speed/ temp/ A/C settings.

[BobT]

I'm assuming that you know in 'auto' mode the interior temp and fan speed is controlled by the thermostat (similar to a house)? If that is the case, then I think what you are saying is that the fan speed isn't reacting to the temp hitting it's set point?

So in mine the fan speed starts off low until the truck warms up a little, then goes to high in order to get it up to temp, and then changes to lower once it is up to the set point. If I have my doors open and it gets cold, it bumps the speed back up, and then back down to maintain.

This is correct. Mine however, intermittently stays in high speed even after the interior temperature reaches set point. I can't manually slow it down but the computer does recognize that I am trying because the display reacts accordingly. It shows a bar symbol similar to what our cell phones show for signal strength.

I I leave it alone long enough, eventually I will hear the fan speed suddenly drop and things work normal again plus I have manual control back. Whatever is keeping the fan speed at high finally lets it go.

I can sometimes get it to work if I shut off the system for 10-20 seconds and then restart. Almost as if it reboots and works again but this doesn't always work.

[BobT]

This might sound dumb but if its in full auto mode (fan speed and temp). then you decrease fan speed, the Cabin temp wont keep up. In My moms Honda it does a similar thing with the fan speed if you turn speed down manually but keep temp on auto (it over rides the driver input) but theres a separate AUTO on/off button that fixes that. manual mode also allows you to turn the a/c compressor off. I see your problem may be different but in the honda at least. auto means you pick the temp, the car maintains that temp regardless until auto mode is turned off, which returns full manual fan speed/ temp/ A/C settings.

It's a combination of temperature and fan speed that are controlled. As the interior gets closer to setpoint, the temperature setting may be lowered and the fan speed may be reduced just to the point where the interior temp can be maintained. Naturally, these two components must offset any temperature loss so the colder it gets outside the hotter or faster the incoming air must be to keep up.

[BobT]

Have the codes checked in the eatc module. Sounds like a bad eatc module to me

I was afraid I'd hear something like this. Any idea of cost?

With it being so intermittent I'm hesitant to take it in. I suspect they won't be able to narrow it down until it stops working 100%. I know how difficult intermittent problems can be on known functional systems.

[Scott K]

I would bring it to a Ford dealer, there is an update for intermiten no communications with a scan tool, and it will also not alow you to change functions with it. The tsb # is 08-26-11, this may, or not be your problem, but I would start with the reprogram first.

There are a few different options on the EATC modules, but here is Fords "LIST" prices. If you shop around, you can usually find a much better price, then Fords LIST prices.

[delcecchi]

How come it takes half an hour less if the vehicle is under warrantee?

[Scott K]

Dealers get paid about 60% of time from the Manufacturer, because they do mass amounts of work with the dealers.

For example, for a month, a dealer may charge Ford 1000 hours of labor for warranty repairs, so get a discount. Plus, as the vehicle ages, and isnt under warranty any more, bolts rust, and things just dont come apart as easy.

It kinda hoses the mechanic in the dealer as well, being most work off of commission.

[JOHNBIGDOG]

Check DTCs.

But you MAY have a bad blower motor Speed controll module.